Photofragment excitation spectrum for O(1D) from the photodissociation of jet-cooled ozone in the wavelength range 305–329 nm

Abstract

The photofragment excitation (PHOFEX) spectrum for O(1D) production from the photolysis of ozone under supersonic free-jet conditions was measured, scanning the photodissociation wavelength in the region of 305–329 nm and probing the O(1D) atoms by vacuum ultraviolet laser induced fluorescence at 115.2 nm. The bond dissociation energy D00(O2–O) was determined to be 101.53±0.25 kJ mol−1 from the cut-off wavelength in the PHOFEX spectrum for the photodissociation of jet-cooled ozone (Trot≈5 K) to O(1D)+O2(a 1Δg). The cut-off wavelength for vibrationally hot band excitation to the dissociative continuum of O(1D)+O2(a 1Δg) was also observed in the PHOFEX spectrum. It was found that the active mode for the hot band excitation was the antisymmetric stretching mode ν3 in the ground electronic state of ozone. Sharp peaks corresponding to vibrational bands in the Huggins system were also observed in the PHOFEX spectrum of the O(1D) atoms produced via the spin-forbidden dissociation process, O(1D)+O2(X 3∑g−). The spectral widths of the vibronic bands in the Huggins system are discussed in terms of the dissociation dynamics.